1. Field of the Invention
This invention relates in general to magnetic transducers, and more particularly to a method and apparatus for forming a high conductance, high aspect ratio structure in a single low temperature copper chemical vapor deposition step.
2. Description of Related Art
Magnetic recording is a key and invaluable segment of the information-processing industry. While the basic principles are one hundred years old for early tape devices, and over forty years old for magnetic hard disk drives, an influx of technical innovations continues to extend the storage capacity and performance of magnetic recording products. For hard disk drives, the areal density or density of written data bits on the magnetic medium has increased by a factor of more than two million since the first disk drive was applied to data storage. Since 1991, areal density has grown by the well-known 60% compound growth rate, and this is based on corresponding improvements in heads, media, drive electronics, and mechanics.
Magnetic recording heads have been considered the most significant factor in areal-density growth. The ability of these components to both write and subsequently read magnetically recorded data from the medium at data densities well into the Gbits/in2 range gives hard disk drives the power to remain the dominant storage device for many years to come.
A disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm above the rotating disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly mounted on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk, or a non-contact location, when the disk is not rotating. However, when the disk rotates, air is compressed by the rotating disk adjacent the ABS causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. The write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
Prior to 1991, heads were designed with a single inductive sensor performing both reading and writing functions. The decreasing signal amplitude resulting from areal densities exceeding 500 Mbits/in2 promoted the development of magnetoresistive and giant-magnetoresistive read sensors merged with an inductive head, which now performed a write function only. While write track widths can be wider than the corresponding read widths, i.e. “write wide and read narrow”, inductive sensors must be redesigned with narrower gaps and pole geometries. At these higher data densities, pole edge effects become more significant. Coil widths and numbers of turns, all attained by advanced photolithographic techniques over large topographies, must be optimized to achieve adequate inductance focused within a very small writing area on the medium. Finally, it is a consequence of increased areal density that the media or internal data rate, i.e. the rate at which information is written and read within a disk drive, is increased.
A write head includes a coil layer embedded in insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A write gap layer between the first and second pole piece layers forms a magnetic gap at an air bearing surface (ABS) of the write head. The pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic field across the magnetic gap between the pole pieces. This field fringes across the magnetic gap for the purpose of writing information in tracks on moving media, such as the circular tracks on the aforementioned rotating disk or a linearly moving magnetic tape in a tape drive.
The drive for micro mechanical structures to consume less area demands high aspect ratios (height over width). The simplest illustration of this is the coil. To allow the same current to be passed through the coil the cross sectional area of the turns must be held constant. As the line width of the coil turns becomes smaller the height must increase to maintain the cross sectional area. Fabricating high aspect ratio copper coils, as used in the magnetic inductive write head, is becoming increasingly more difficult to create using tradition electroplating on top of a copper containing a seed layer. Further, it is difficult to use electroplating to produce a conformal seed layer that minimizes discontinuities. These seed layers are not always continuous or plating tends to produce voids in high aspect ration structures.
These coils were traditionally produced via plating through a resist mask over a full film copper seed layer where the seed layer would be physically removed in a later process. However, removal of the seed has become difficult with sub-micron spacing between the coils. Thus, an alternate method is to use a damascene process to produce the coils. Nevertheless, this process is dependent on seed layer, plating without voids, and planarization of the wafer.
It can be seen that there is a need to introduce a structure or mechanism that maintains a void free deposition of a conductive material to increase conductance of a coil structure.